LsRedy, I know someone at MAC had told you this but it's a really, really poor excuse and just another indication of how inept the company really is. I dont doubt that the person who told you this believes what he is saying. Like many corporations, the BS is fabricated at the top and fed to the little guys in the trenches.
Their have been a few isolated cases of other DOHC's smoking after other companies LT's were installed. Now, it is not inconceivable that their was an occasional quality control issue with their coatings also, but MAC is the only company who consistently has problems.
I guarantee you, headers costing several thousands of dollars which incorporate the latest and greatest technology, do not cause the problems MAC is trying to pawn off. Never, in the history of hot rodding, has their been a case of headers being so efficient that they literally "suck" oil past the valve guide seals. Nobody is convinced that MACs mass produced, off the shelf cheapo header is going to eclipse the exhaust technology designed into Winston Cup and other professional racing venues.
The damage has been witnessed first hand by several reputable, long term posters on the various boards and it doesnt just go away after the MACs are removed. It is visible, and quantifiable cylinder damage.
Now MAC has this new coating. Gee, I wonder why. It only took them six years and several wasted motors to fix a simple application flaw. I wouldnt care if they made the best product in the world for our Cobras, I would not support them.
Todd